Solicitors for Andy Harrison have contacted us since publication to say that a number of the statements made in this article are "untrue and defamatory" of him. They have referred us in particular to the Chairman's statement in easyJet's annual report for 2009 where he says that the "Company has delivered a resilient performance in what has been one of the most challenging trading environments for many years" and thanks "Andy Harrison and his executive team for so successfully managing the Company during such a challenging year".

Sir Stelios Haji-Ioannou shattered a fragile boardroom truce at easyJet today by giving the carrier's chief executive, Andy Harrison, a valedictory broadside in which he described him as overrated. The tycoon, whose family owns a third of the low-cost carrier, also accused Harrison of "squandering" $4bn (£2.7bn) on an Airbus aircraft deal that was in fact signed by his predecessor.

Harrison, who leaves next month for the top job at leisure group Whitbread, said easyJet's performance would "do the talking" as one of only two European carriers to report a pre-tax and post-tax profit last year.

Haji-Ioannou clashed with board members 18 months ago when the carrier's largest shareholder warned that the business was expanding too fast into a deep downturn. A truce was established last year, but a wave of senior departures indicated ongoing tensions. In December last year Harrison became the fifth of easyJet's eight-person management board to quit in 12-months.

The latest attack focused on Harrison's remuneration, including a £1m bonus last year, the board's failure to pay a dividend and easyJet's share price performance since he joined in December 2005 from the RAC. A source close to Haji-Ioannou said: "Harrison's performance is over-rated. Over the last five years he developed a love affair with Airbus, squandered $4bn and doubled the size of the fleet, while he paid no dividends and the share price has gone sideways. The only thing that went up was the size of his bonus."

EasyJet brushed off the latest intervention from its biggest investor, pointing to a share price that was 330p when Harrison joined and 435p this morning, adding that easyJet's fleet was 122 in 2005, 189 now and will be 208 in 2012. A spokesman said the October 2002 Airbus order was signed by then chief executive Ray Webster and was not challenged by Haji-Ioannou, then easyJet chairman.

Harrison starts at Whitbread, the owner of Premier Inn and Costa Coffee, next month and will be replaced by Carolyn McCall, chief executive of Guardian Media Group, which publishes the Guardian. Asked this year if she was happy with the strategy agreed between Haji-Ioannou and the board, McCall said: "I think we need to look forward now and build on what they've agreed." However, the Haji-Ioannou camp could not resist a dig at Whitbread shareholders, warning them that Harrison's philosophy would result in no dividend, a stagnant share price and "a contract to build 300 Premier Inns on the continent". Harrison declined to comment.

The latest salvo overshadowed results for the six months to 31 March, which saw easyJet reduce its loss during the first half – when it traditionally loses money – from £116.5m to £78.7m. Revenues rose 13% to £1.2bn with turnover from add-ons such as bag check-in charges rising by 21% to £258.3m. EasyJet added that the loss from a six-day shutdown of UK airspace last month, due to volcanic ash, would be up to £75m, slashing the expected full-year profit range of £175m-£200m to £100m-£150m.